1. Field of the Invention
The present invention relates to a technique for enabling a digital computer system to easily change its operating system or working mode and, more particularly, to a technique for enabling a digital computer system to easily change its operating system while under a different operating system or to easily change its working mode under the same operating system.
2. Description of the Related Art
Many kinds of operating systems may be used in one digital computer system due to the widespread use and applications of a computer in which the necessary application programs under each operating system are executed. Thus, changing the operating system is needed.
For example, in personal computers (PCS), changing the operating system is effected between executing application programs under a disk operating system (DOS) of a text mode and executing application programs under Windows 95 or 98, a PC function and a settop box function, a PC function and a network terminal function, and a PC function and a television function.
Earlier digital computer systems included: a CPU (central processing unit); a RAM (random access memory) for temporarily storing the system software and user software executed by the CPU (central processing unit); a ROM (read only memory) for storing system initialization programs executed by the CPU (central processing unit); a RTC (real time clock) which stores information of a time calculation and a system composition; a bus which transmits information to each element with connecting elements; a user interface having a display unit and a keyboard; a serial/parallel peripheral device having an RS-232C interface unit and a printer; an auxiliary memory having a floppy disk drive and a hard disk drive; an interface controller having a display controller and a keyboard controller; a serial/parallel port having a serial interface and a parallel interface; and an auxiliary memory controller having a floppy disk drive controller and a hard disk drive controller.
If power is supplied to the computer system, the CPU executes an initialization process so that the hardware elements, such as the RAM, the user interface controller, and the auxiliary memory controller, are operated by a control program within the ROM, and a self-test process is executed in order to examine whether each hardware element is operating normally.
The control program is a POST (power on self test) of a BIOS (basic input output system) program within the ROM in a personal computer.
When the above process is over, the CPU loads a boot program, which is loaded from a specific place in the auxiliary memory, such as the floppy disk drive or the hard disk drive, into the RAM by a bootstrap loader within the control program, and executes the boot program.
While the boot program executes, an user executes an application program by selecting one operating system, that is, one operating system from among many kinds of operating systems.
The boot program loads the operating system selected by the user into the RAM, and the it operating system executes an operating system initialization process in a computer system and remains in a wait state to receive an instruction from the user.
When in the wait state, the user inputs instructions and executes the work to be done by executing an application program. And, when the work is terminated, the operating system shutdown procedure is executed to escape the operating system.
However, the above shutdown procedure need not be executed in an operating system such as DOS.
At last, the user turns the power off and all the work is terminated.
It takes a long time to execute a specific application program. The instructions must be input again and again in order to execute an application program.
When the power of the computer system is turned off during an operation, the above operation is needed in order to restore the power and to repeat the operation.
When an application is to be executed under another operating system, the above operation needs to be repeated.
U.S. Pat. No. 5,297,282, to Meilak et al., entitled Resume Processing Function For The OS/2 Operating System discloses an arrangement for storing an operating system in a back-up memory and then utilizing the stored information in a back-up memory to restart the computer upon the power being restored.
The following additional references also bear features in common with the present invention: U.S. Pat. No. 5,278,973 to O'Brien et al., entitled Dual Operating System Computer, U.S. Pat. No. 5,327,531 to Bealkowski, entitled Data Processing System Including Corrupt Flash ROM Recovery, U.S. Pat. No. 5,355,498 to Provino, et al., entitled Method And Apparatus For Booting A Computer System Without Loading A Device Driver Into Memory, U.S. Pat. No. 5,386,565 to Tanaka et al., entitled Method And System For Controlling/Monitoring Computer System Having Plural Operating Systems To Run Thereon, U.S. Pat. No. 5,414,860 to Canova Jr. et al., entitled Power Management Initialization For A Computer Operable Under A Plurality Of Operating Systems, U.S. Pat. No. 5,432,935 to Kato et al., entitled Emulation For Executing A Second Language Application Program On A Computer Having A First Language Operating System, U.S. Pat. No. 5,432,939 to Blackledge Jr. et al., entitled Trusted Personal Computer System With Management Control Over Initial Program Loading, U.S. Pat. No. 5,481,714 to Pipkin et al., entitled Method And System for Installing An Operating System On A Data Processing System With Abort Capability And voice Input Feature, U.S. Pat. No. 5,483,647 to Yu et al., entitled System For Switching Between Two Different Operating Systems By Invoking The Server To Determine Physical Conditions To Initiate A Physical Connection Transparent To The User, U.S. Pat. No. 5,487,161 to Koenck et al., entitled Computerized Data Terminal With Switchable Memory Address For Start-Up And System Control Instructions, U.S. Pat. No. 5,546,585 to Soga, entitled Personal Computer System With Start-Up Capability From An External Mass Storage Device, U.S. Pat. No. 5,557,777 to Culbert, entitled Method And Apparatus For System Recovery From Power Loss, U.S. Pat. No. 5,386,552 to Garney, entitled Preservation Of A computer System Processing State In A Mass Storage Device, U.S. Pat. No. 5,664,203 to Hong et al., entitled Peripheral Device Input-Initiated Resume System For combined Hibernation System And Back-Up Power Supply For Computer, U.S. Pat. No. 5,710,930 to Laney et al., entitled Apparatus And A Method For Allowing An Operating System Of A Computer System To Persist A Cross A Power Off And On Cycle, U.S. Pat. No. 5,708,820 to Park et al., entitled Network Hibernation System For Suspending And Resuming Operation Of Computer System Operable In Network Environment In Event Of Power Failure Or Period Of Inactivity, U.S. Pat. No. 5,410,713 to White et al., entitled Power-Management System For A Computer, U.S. Pat. No. 4,675,814 to Murai et al., entitled Method Of Switching Operating Systems For A Data Processing System, U.S. Pat. No. 4,493,034 to Angelle et al., entitled Apparatus And Method For An Operating System Supervisor In A Data Processing System, and U.S. Pat. No. 5,715,464 to Crump et al., entitled Computer System Having Suspend Once Resume Many Sessions.